-
+
Functions and Operators
]]>
+
- 3>
+ 2>
XML Predicates
+ The expressions described in this section check properties
+ of xml values.
+
+
+
+
IS DOCUMENT
+
between documents and content fragments.
+
+
+
XMLEXISTS
+
+
+
+
+
+XMLEXISTS(text PASSING BY REF xml BY REF)
+
+
+ The function xmlexists returns true if the
+ XPath expression in the first argument returns any nodes, and
+ false otherwise. (If either argument is null, the result is
+ null.)
+
+
+ Example:
+
+SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF 'TorontoOttawa');
+
+ xmlexists
+------------
+ t
+(1 row)
+]]>
+
+
+ The BY REF clauses have no effect in
+ PostgreSQL, but are allowed for SQL conformance and compatibility
+ with other implementations. Per SQL standard, the
+ first BY REF is required, the second is
+ optional. Also note that the SQL standard specifies
+ the xmlexists construct to take an XQuery
+ expression as first argument, but PostgreSQL currently only
+ supports XPath, which is a subset of XQuery.
+
+
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.714 2010/07/25 23:21:21 rhaas Exp $
+ * $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.715 2010/08/05 04:21:53 petere Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
%type xml_attribute_el
%type xml_attribute_list xml_attributes
%type xml_root_version opt_xml_root_standalone
+%type xmlexists_argument
%type document_or_content
%type xml_whitespace_option
OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR
ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
- PARSER PARTIAL PARTITION PASSWORD PLACING PLANS POSITION
+ PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POSITION
PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
PRIOR PRIVILEGES PROCEDURAL PROCEDURE
QUOTE
- RANGE READ REAL REASSIGN RECHECK RECURSIVE REFERENCES REINDEX
+ RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REINDEX
RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA RESET RESTART
RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROW ROWS RULE
WHEN WHERE WHITESPACE_P WINDOW WITH WITHOUT WORK WRAPPER WRITE
- XML_P XMLATTRIBUTES XMLCONCAT XMLELEMENT XMLFOREST XMLPARSE
+ XML_P XMLATTRIBUTES XMLCONCAT XMLELEMENT XMLEXISTS XMLFOREST XMLPARSE
XMLPI XMLROOT XMLSERIALIZE
YEAR_P YES_P
{
$$ = makeXmlExpr(IS_XMLELEMENT, $4, $6, $8, @1);
}
+ | XMLEXISTS '(' c_expr xmlexists_argument ')'
+ {
+ /* xmlexists(A PASSING [BY REF] B [BY REF]) is
+ * converted to xmlexists(A, B)*/
+ FuncCall *n = makeNode(FuncCall);
+ n->funcname = SystemFuncName("xmlexists");
+ n->args = list_make2($3, $4);
+ n->agg_order = NIL;
+ n->agg_star = FALSE;
+ n->agg_distinct = FALSE;
+ n->func_variadic = FALSE;
+ n->over = NULL;
+ n->location = @1;
+ $$ = (Node *)n;
+ }
| XMLFOREST '(' xml_attribute_list ')'
{
$$ = makeXmlExpr(IS_XMLFOREST, NULL, $3, NIL, @1);
| /*EMPTY*/ { $$ = FALSE; }
;
+/* We allow several variants for SQL and other compatibility. */
+xmlexists_argument:
+ PASSING c_expr
+ {
+ $$ = $2;
+ }
+ | PASSING c_expr BY REF
+ {
+ $$ = $2;
+ }
+ | PASSING BY REF c_expr
+ {
+ $$ = $4;
+ }
+ | PASSING BY REF c_expr BY REF
+ {
+ $$ = $4;
+ }
+ ;
+
+
/*
* Window Definitions
*/
| PARSER
| PARTIAL
| PARTITION
+ | PASSING
| PASSWORD
| PLANS
| PRECEDING
| REASSIGN
| RECHECK
| RECURSIVE
+ | REF
| REINDEX
| RELATIVE_P
| RELEASE
| XMLATTRIBUTES
| XMLCONCAT
| XMLELEMENT
+ | XMLEXISTS
| XMLFOREST
| XMLPARSE
| XMLPI
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.98 2010/07/06 19:18:58 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.99 2010/08/05 04:21:54 petere Exp $
*
*-------------------------------------------------------------------------
*/
/*
- * Evaluate XPath expression and return array of XML values.
+ * Common code for xpath() and xmlexists()
*
- * As we have no support of XQuery sequences yet, this function seems
- * to be the most useful one (array of XML functions plays a role of
- * some kind of substitution for XQuery sequences).
+ * Evaluate XPath expression and return number of nodes in res_items
+ * and array of XML values in astate.
*
* It is up to the user to ensure that the XML passed is in fact
* an XML document - XPath doesn't work easily on fragments without
* a context node being known.
*/
-Datum
-xpath(PG_FUNCTION_ARGS)
-{
#ifdef USE_LIBXML
- text *xpath_expr_text = PG_GETARG_TEXT_P(0);
- xmltype *data = PG_GETARG_XML_P(1);
- ArrayType *namespaces = PG_GETARG_ARRAYTYPE_P(2);
- ArrayBuildState *astate = NULL;
+static void
+xpath_internal(text *xpath_expr_text, xmltype *data, ArrayType *namespaces,
+ int *res_nitems, ArrayBuildState **astate)
+{
xmlParserCtxtPtr ctxt = NULL;
xmlDocPtr doc = NULL;
xmlXPathContextPtr xpathctx = NULL;
xmlChar *string;
xmlChar *xpath_expr;
int i;
- int res_nitems;
int ndim;
Datum *ns_names_uris;
bool *ns_names_uris_nulls;
* ARRAY[ARRAY['myns', 'http://example.com'], ARRAY['myns2',
* 'http://example2.com']].
*/
- ndim = ARR_NDIM(namespaces);
+ ndim = namespaces ? ARR_NDIM(namespaces) : 0;
if (ndim != 0)
{
int *dims;
xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
"invalid XPath expression");
+ /*
+ * Version 2.6.27 introduces a function named
+ * xmlXPathCompiledEvalToBoolean, which would be enough for
+ * xmlexists, but we can derive the existence by whether any
+ * nodes are returned, thereby preventing a library version
+ * upgrade and keeping the code the same.
+ */
xpathobj = xmlXPathCompiledEval(xpathcomp, xpathctx);
if (xpathobj == NULL) /* TODO: reason? */
xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
/* return empty array in cases when nothing is found */
if (xpathobj->nodesetval == NULL)
- res_nitems = 0;
+ *res_nitems = 0;
else
- res_nitems = xpathobj->nodesetval->nodeNr;
+ *res_nitems = xpathobj->nodesetval->nodeNr;
- if (res_nitems)
+ if (*res_nitems && astate)
{
+ *astate = NULL;
for (i = 0; i < xpathobj->nodesetval->nodeNr; i++)
{
Datum elem;
bool elemisnull = false;
elem = PointerGetDatum(xml_xmlnodetoxmltype(xpathobj->nodesetval->nodeTab[i]));
- astate = accumArrayResult(astate, elem,
- elemisnull, XMLOID,
- CurrentMemoryContext);
+ *astate = accumArrayResult(*astate, elem,
+ elemisnull, XMLOID,
+ CurrentMemoryContext);
}
}
}
xmlXPathFreeContext(xpathctx);
xmlFreeDoc(doc);
xmlFreeParserCtxt(ctxt);
+}
+#endif /* USE_LIBXML */
+
+/*
+ * Evaluate XPath expression and return array of XML values.
+ *
+ * As we have no support of XQuery sequences yet, this function seems
+ * to be the most useful one (array of XML functions plays a role of
+ * some kind of substitution for XQuery sequences).
+ */
+Datum
+xpath(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+ text *xpath_expr_text = PG_GETARG_TEXT_P(0);
+ xmltype *data = PG_GETARG_XML_P(1);
+ ArrayType *namespaces = PG_GETARG_ARRAYTYPE_P(2);
+ int res_nitems;
+ ArrayBuildState *astate;
+
+ xpath_internal(xpath_expr_text, data, namespaces,
+ &res_nitems, &astate);
if (res_nitems == 0)
PG_RETURN_ARRAYTYPE_P(construct_empty_array(XMLOID));
return 0;
#endif
}
+
+/*
+ * Determines if the node specified by the supplied XPath exists
+ * in a given XML document, returning a boolean.
+ */
+Datum xmlexists(PG_FUNCTION_ARGS)
+{
+#ifdef USE_LIBXML
+ text *xpath_expr_text = PG_GETARG_TEXT_P(0);
+ xmltype *data = PG_GETARG_XML_P(1);
+ int res_nitems;
+
+ xpath_internal(xpath_expr_text, data, NULL,
+ &res_nitems, NULL);
+
+ PG_RETURN_BOOL(res_nitems > 0);
+#else
+ NO_XML_SUPPORT();
+ return 0;
+#endif
+}
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.588 2010/07/16 02:15:54 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.589 2010/08/05 04:21:54 petere Exp $
*
*-------------------------------------------------------------------------
*/
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 201007151
+#define CATALOG_VERSION_NO 201008051
#endif
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.573 2010/07/29 20:09:25 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.574 2010/08/05 04:21:54 petere Exp $
*
* NOTES
* The script catalog/genbki.pl reads this file and generates .bki
DATA(insert OID = 2932 ( xpath PGNSP PGUID 14 1 0 0 f f f t f i 2 0 143 "25 142" _null_ _null_ _null_ _null_ "select pg_catalog.xpath($1, $2, ''{}''::pg_catalog.text[])" _null_ _null_ _null_ ));
DESCR("evaluate XPath expression");
+DATA(insert OID = 2614 ( xmlexists PGNSP PGUID 12 1 0 0 f f f t f i 2 0 16 "25 142" _null_ _null_ _null_ _null_ xmlexists _null_ _null_ _null_ ));
+DESCR("test XML value against XPath expression");
+
/* uuid */
DATA(insert OID = 2952 ( uuid_in PGNSP PGUID 12 1 0 0 f f f t f i 1 0 2950 "2275" _null_ _null_ _null_ _null_ uuid_in _null_ _null_ _null_ ));
DESCR("I/O");
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/include/parser/kwlist.h,v 1.12 2010/02/12 17:33:21 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/parser/kwlist.h,v 1.13 2010/08/05 04:21:54 petere Exp $
*
*-------------------------------------------------------------------------
*/
PG_KEYWORD("parser", PARSER, UNRESERVED_KEYWORD)
PG_KEYWORD("partial", PARTIAL, UNRESERVED_KEYWORD)
PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD)
+PG_KEYWORD("passing", PASSING, UNRESERVED_KEYWORD)
PG_KEYWORD("password", PASSWORD, UNRESERVED_KEYWORD)
PG_KEYWORD("placing", PLACING, RESERVED_KEYWORD)
PG_KEYWORD("plans", PLANS, UNRESERVED_KEYWORD)
PG_KEYWORD("reassign", REASSIGN, UNRESERVED_KEYWORD)
PG_KEYWORD("recheck", RECHECK, UNRESERVED_KEYWORD)
PG_KEYWORD("recursive", RECURSIVE, UNRESERVED_KEYWORD)
+PG_KEYWORD("ref", REF, UNRESERVED_KEYWORD)
PG_KEYWORD("references", REFERENCES, RESERVED_KEYWORD)
PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD)
PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD)
PG_KEYWORD("xmlattributes", XMLATTRIBUTES, COL_NAME_KEYWORD)
PG_KEYWORD("xmlconcat", XMLCONCAT, COL_NAME_KEYWORD)
PG_KEYWORD("xmlelement", XMLELEMENT, COL_NAME_KEYWORD)
+PG_KEYWORD("xmlexists", XMLEXISTS, COL_NAME_KEYWORD)
PG_KEYWORD("xmlforest", XMLFOREST, COL_NAME_KEYWORD)
PG_KEYWORD("xmlparse", XMLPARSE, COL_NAME_KEYWORD)
PG_KEYWORD("xmlpi", XMLPI, COL_NAME_KEYWORD)
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.31 2010/03/03 17:29:45 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/xml.h,v 1.32 2010/08/05 04:21:54 petere Exp $
*
*-------------------------------------------------------------------------
*/
extern Datum xmltotext(PG_FUNCTION_ARGS);
extern Datum xmlvalidate(PG_FUNCTION_ARGS);
extern Datum xpath(PG_FUNCTION_ARGS);
+extern Datum xmlexists(PG_FUNCTION_ARGS);
extern Datum table_to_xml(PG_FUNCTION_ARGS);
extern Datum query_to_xml(PG_FUNCTION_ARGS);
{two,etc}
(1 row)
+-- Test xmlexists evaluation
+SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF 'Bidford-on-AvonCwmbranBristol');
+ xmlexists
+-----------
+ f
+(1 row)
+
+SELECT xmlexists('//town[text() = ''Cwmbran'']' PASSING BY REF 'Bidford-on-AvonCwmbranBristol');
+ xmlexists
+-----------
+ t
+(1 row)
+
+INSERT INTO xmltest VALUES (4, '
'::xml);
+INSERT INTO xmltest VALUES (5, '
'::xml);
+INSERT INTO xmltest VALUES (6, 'BudvarfreeCarlinglots'::xml);
+INSERT INTO xmltest VALUES (7, 'MolsonfreeCarlinglots'::xml);
+SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beer' PASSING data);
+ count
+-------
+ 0
+(1 row)
+
+SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beer' PASSING BY REF data BY REF);
+ count
+-------
+ 0
+(1 row)
+
+SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers' PASSING BY REF data);
+ count
+-------
+ 2
+(1 row)
+
+SELECT COUNT(id) FROM xmltest WHERE xmlexists('/menu/beers/name[text() = ''Molson'']' PASSING BY REF data);
+ count
+-------
+ 1
+(1 row)
+
+CREATE TABLE query ( expr TEXT );
+INSERT INTO query VALUES ('/menu/beers/cost[text() = ''lots'']');
+SELECT COUNT(id) FROM xmltest, query WHERE xmlexists(expr PASSING BY REF data);
+ count
+-------
+ 2
+(1 row)
+
^
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.
+-- Test xmlexists evaluation
+SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF 'Bidford-on-AvonCwmbranBristol');
+ERROR: unsupported XML feature
+LINE 1: ...sts('//town[text() = ''Toronto'']' PASSING BY REF '
+ ^
+DETAIL: This functionality requires the server to be built with libxml support.
+HINT: You need to rebuild PostgreSQL using --with-libxml.
+SELECT xmlexists('//town[text() = ''Cwmbran'']' PASSING BY REF 'Bidford-on-AvonCwmbranBristol');
+ERROR: unsupported XML feature
+LINE 1: ...sts('//town[text() = ''Cwmbran'']' PASSING BY REF '
+ ^
+DETAIL: This functionality requires the server to be built with libxml support.
+HINT: You need to rebuild PostgreSQL using --with-libxml.
+INSERT INTO xmltest VALUES (4, '
'::xml);
+ERROR: unsupported XML feature
+LINE 1: INSERT INTO xmltest VALUES (4, '
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